Image projection apparatus

ABSTRACT

An image projection apparatus for projecting an image on a projection plane includes a light source; a light source housing to encase the light source; a ventilation unit to send air to the light source; and a flow path set between the light source housing and a side face of the image projection apparatus. A part of the air sent to the light source, by using the ventilation unit, is flowed into the flow path.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority pursuant to 35 U.S.C. §119 to JapanesePatent Application No. 2012-062108, filed on Mar. 19, 2012 in the JapanPatent Office, the disclosure of which is incorporated by referenceherein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to an image projection apparatus.

2. Background Art

Image projection apparatuses such as projectors can receive image datafrom personal computers or video cameras to generate an image by usingan image generator. The image generator projects and displays the imageonto a screen using light emitted from a light source.

The light source of the image projection apparatus may be a halogenlamp, a metal-halide lamp, or a high-pressure mercury vapor lamp, all ofwhich generate heat when they emit light. Therefore, a ventilation unitsuch as a blower or a fan is used to cool the light source as disclosedin JP-2003-5292-A and WO-02/097529-A.

However, the maximum temperature of the light source become, forexample, 1000 Celcius degrees, by which the temperature of a lightsource housing that encases the light source in a body of the imageprojection apparatus also becomes high temperature. Such heated lightsource housing causes the high temperature of a side face of the imageprojection apparatus such as an outer cover facing the light sourcehousing. If a user touches such hot outer cover, the user may feel suchhot outer cover uncomfortable. Therefore, in addition to the ventilationunit to send air to the light source, another ventilation unit to sendair to a space between the outer cover and the light source housing maybe disposed. However, such another ventilation unit will increase thenumber of parts, and increasing cost and size of the apparatus.

SUMMARY

As one aspect of the present invention, an image projection apparatusfor projecting an image on a projection plane is devised. The imageprojection apparatus includes a light source; a light source housing toencase the light source; a ventilation unit to send air to the lightsource; and a flow path set between the light source housing and a sideface of the image projection apparatus. A part of the air sent to thelight source, by using the ventilation unit, is flowed into the flowpath.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 shows a perspective view of a projector according to an exampleembodiment and a projection plane;

FIG. 2 shows a pattern of light paths from a projector to a projectionplane;

FIG. 3 shows a schematic perspective view of a projector;

FIG. 4 shows a perspective view of a main unit of a projector;

FIG. 5 shows a perspective view of an image generation unit;

FIG. 6 shows a schematic perspective view of a light source unit;

FIG. 7 shows a perspective view of an image generation unit and alighting unit;

FIG. 8 shows a perspective view of the image generation unit of FIG. 7;

FIG. 9 shows a perspective view of a first optical unit with thelighting unit and the image generation unit;

FIG. 10 shows a cross-sectional view along a line D-D of FIG. 9;

FIG. 11 shows a perspective view of a second optical unit configuredwith a projection lens unit, the lighting unit, and the image generationunit;

FIG. 12 shows a perspective view of the second optical unit configuredwith the first optical unit, the lighting unit, and the image generationunit;

FIG. 13 shows a schematic view of the light path from the first opticalsystem to a projection plane;

FIG. 14 schematically shows a layout of units in the projector;

FIG. 15 shows an example of use environment of the projector accordingto an example embodiment;

FIG. 16 shows an example of use environment of a conventional projector;

FIG. 17 shows another example of use environment of a conventionalprojector;

FIG. 18 shows an example of another use environment of the projectoraccording to an example embodiment;

FIG. 19 shows a perspective view of the projector viewed from a bottomface of the projector;

FIG. 20 shows a perspective view of the projector when an openablyclosable cover is removed from the projector;

FIG. 21 shows a schematic view of airflow patterns in the projector;

FIG. 22 shows an internal configuration of the projector of FIG. 21;

FIG. 23 shows a cross-sectional view of the projector cut at a line E-Eof FIG. 22;

FIG. 24 shows a perspective view of the projector by removing an outercover; and

FIG. 25 shows a cross-sectional view of a light source housing and itssurroundings of the projector.

The accompanying drawings are intended to depict exemplary embodimentsof the present invention and should not be interpreted to limit thescope thereof. The accompanying drawings are not to be considered asdrawn to scale unless explicitly noted, and identical or similarreference numerals designate identical or similar components throughoutthe several views.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description is now given of exemplary embodiments of the presentinvention. It should be noted that although such terms as first, second,etc. may be used herein to describe various elements, components,regions, layers and/or sections, it should be understood that suchelements, components, regions, layers and/or sections are not limitedthereby because such terms are relative, that is, used only todistinguish one element, component, region, layer or section fromanother region, layer or section. Thus, for example, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

In addition, it should be noted that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the present invention. Thus, for example, asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Moreover, the terms “includes” and/or “including”, when usedin this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Furthermore, although in describing views shown in the drawings,specific terminology is employed for the sake of clarity, the presentdisclosure is not limited to the specific terminology so selected and itis to be understood that each specific element includes all technicalequivalents that have the same function, operate in a similar manner andachieve a similar result. Referring now to the drawings, an apparatus orsystem according to an example embodiment is described hereinafter.

FIG. 1 shows a perspective view of a projector 1 and a projection plane101. The projector 1 includes, for example, a transparent glass 51, anoperation unit 83, and a focus lever 33. As shown in FIG. 1, theprojector 1 has the transparent glass 51 on its top face, from which aprojection image P is projected to the projection plane 101. Theprojection image P projected from the transparent glass 51 is displayedon the projection plane 101 such as a screen. Further, the projector 1has the operation unit 83 on its top face, by which a user can operatethe projector 1. Further, the projector 1 has the focus lever 33 on itsside face for adjusting the focus of image. Hereinafter, the normal linedirection of the projection plane 101 is set as X direction, the shortside direction of the projection plane 101 (or top/bottom direction) isset as Y direction, and the long side direction of the projection plane101 (or horizontal direction) is set as Z direction.

FIG. 2 shows a pattern of light paths from the projector 1 to theprojection plane 101. The projector 1 includes, for example, a lightsource unit having a light source, and an image generator A to generateimages using the light emitted from the light source. The imagegenerator A includes, for example, an image generation unit 10, and alighting unit 20. The projector 1 further includes a projection opticalsystem B.

The image generation unit 10 includes an image generation element suchas a digital mirror device (DMD) 12. The lighting unit 20 reflects andirradiates light coming from the light source to the DMD 12 to generatea light image. The projection optical system B projects the light imageon the projection plane 101. The projection optical system B includes aleast one pass-through type reflection optical system. For example, theprojection optical system B includes a first optical unit 30 and asecond optical unit 40.

The first optical unit 30 includes, for example, a first optical system70 of co-axial system having the positive power. The second optical unit40 includes, for example, a reflection mirror 41, and a curved mirror 42having the positive power.

The DMD 12 can generate an image using the light emitted from the lightsource. Specifically, the light emitted from the light source irradiatesthe DMD 12 and an image is generated by modulating the light irradiatedby the lighting unit 20. The image generated by the DMD 12 is projectedonto the projection plane 101 via the first optical system 70 of thefirst optical unit 30, and the reflection mirror 41 and the curvedmirror 42 of the second optical unit 40.

FIG. 3 shows a schematic perspective view of an internal configurationof the projector 1. As shown in FIG. 3, the image generation unit 10,the lighting unit 20, the first optical unit 30, the second optical unit40 are arranged along the Y direction in FIG. 3. Further, a light sourceunit 60 can be disposed at a right side of the lighting unit 20 in FIG.3.

Further, as shown in FIG. 3, the first optical unit 30 has a lens holder32 having legs 32 a 1 and 32 a 2, and the image generation unit 10 has ascrew stopper 262 used to fix the image generation unit 10 to thelighting unit 20 using a screw.

A description is given of configuration of each unit. Initially, thelight source unit 60 is described. FIG. 4 shows a schematic perspectiveview of the light source unit 60. The light source unit 60 includes alight-source bracket 62, and a light source 61 fixed on the light-sourcebracket 62. The light source 61 is, for example, a halogen lamp, ametal-halide lamp, and a high-pressure mercury vapor lamp. Further, thelight-source bracket 62 has a connector 62 a connectable to apower-source connector of a power source unit 80 (FIG. 14).

Further, a holder 64 is fixed on the light exiting side of the lightsource 61 disposed on the light-source bracket 62 by using screws,wherein the holder 64 retains a reflector or the like. Further, a lightexiting window 63 is disposed for the holder 64 while the light exitingwindow 63 is disposed at a side opposite the position of the lightsource 61. The light emitted from the light source 61 can be guided tothe light exiting window 63 by the reflector retained in the holder 64,and exits from the light exiting window 63.

Further, light source position-setting members 64 a 1 to 64 a 3 aredisposed at the top face of the holder 64 and both ends of the Xdirection of the bottom face of the holder 64 so that the light sourceunit 60 can be positioned correctly on a lighting unit bracket 26 of thelighting unit 20 (FIG. 6). For example, the light sourceposition-setting member 64 a 3 disposed at the top face of the holder 64has a protruded-shape, and the light source position-setting members 64a 1 and 64 a 2 disposed at the bottom face of the holder 64 have a holeshape.

Further, a light-source air intake port 64 b is disposed at a side faceof the holder 64 to take in air used for cooling the light source 61,and a light-source air exhaust port 64 c is disposed at the top face ofthe holder 64 to exhaust air heated by the heat of the light source 61.

Further, a pass-through area 65 is disposed for the light-source bracket62 to take in air sucked in by an air-intake blower 91 (FIG. 20) to bedescribed later. Further, an opening 65 a is disposed at an air-intakeside of the pass-through area 65 as shown in FIG. 4 to send a part ofairflow flowing into the pass-through area 65 to a space between thelight source unit 60 and an openably closable cover 54 (FIG. 19), to bedescribed later. The cooling of the light source unit 60 will bedescribed later.

Further, as shown in FIG. 4, the light source position-setting member 64a 3 having a protruded-shape is provided on a plane face portion 64 d 2disposed at the top face of the holder 64, and the light sourceposition-setting members 64 a 1 and 64 a 2 having the hole shape isdisposed at a plane face portion 64 d 1 of the bottom face of the holder64. Such plane face portion 64 d 2 and the plane face portion 64 d 1 canbe used as abutting members to be abutted to the lighting unit bracket26 when pressed by a pressing member of the openably closable cover 54to be described later.

A description is given of the lighting unit 20 with reference to FIG. 5,which shows a perspective view of optical parts encased in the lightingunit 20 and other units. As shown in FIG. 5, the lighting unit 20includes, for example, a color wheel 21, a light tunnel 22, two relaylenses 23, a cylinder mirror 24, and a concave mirror 25, wherein suchparts can be retained by the lighting unit bracket 26. The lighting unitbracket 26 includes, for example, a casing 261 that encases the relaylenses 23, the cylinder mirror 24, and the concave mirror 25. Among foursides of the casing 261, only one side has a side face (i.e., right sideof FIG. 5), and other three sides are opening. Further, an OFF plate 27(FIG. 6) is disposed at one opening-side of the X direction in FIG. 5,and a cover member is disposed at another opening-side of the Xdirection in FIG. 5. With such a configuration, the relay lenses 23, thecylinder mirror 24, and the concave mirror 25 encased in the casing 261of the lighting unit bracket 26 can be covered by the lighting unitbracket 26, the OFF plate 27, and the cover member.

Further, a through-hole 26 d is disposed on the bottom face of thecasing 261 of the lighting unit bracket 26 so that the DMD 12 can beexposed through the through-hole 26 d.

Further, the lighting unit bracket 26 includes, for example, three legs29. Such legs 29 can contact a base member 53 (FIGS. 13, 18, 19) of theprojector 1 to support the weight of the first optical unit 30 and thesecond optical unit 40 stacked and fixed on the lighting unit bracket26. Further, by providing the legs 29, a space for taking in externalair to a heat exchanger such as a heat sink 13 (FIG. 6) that cools theDMD 12 of the image generation unit 10, can be arranged, to be describedlater.

Further, as shown in FIG. 5, the lens holder 32 of the first opticalunit 30 includes, for example, legs 32 a 3 and 32 a 4, and the secondoptical unit 40 includes, for example, a screw stopper 45 a 3.

FIG. 6 shows a perspective view of the image generation unit 10, thelighting unit 20, and a projection lens unit 31 viewed from thedirection C shown in FIG. 5. The casing 261 of the lighting unit bracket26 has a top face 26 b extending in a direction perpendicular to the Ydirection of FIG. 6. Through-holes are disposed at four corners of thetop face 26 b to fasten the first optical unit 30 with screws byinserting the screws into the through-holes. For example, FIG. 6 showsthe through-holes 26 c 1 and 26 c 2.

Further, as shown in FIG. 6, position-setting holes 26 e 1 and 26 e 2are respectively disposed next to the through-holes 26 c 1 and 26 c 2 toset the first optical unit 30 at a correct position with the lightingunit 20. As for such position-setting holes 26 e 1 and 26 e 2, theposition-setting hole 26 e 1 disposed at the color wheel 21 side is usedas a primary position-setting hole having a circular hole shape, and theposition-setting hole 26 e 2 disposed at an opposite side of the colorwheel 21 is used as a secondary position-setting hole having a slot holeextending in the Z direction.

Further, a position-setting protrusion 26 f is disposed around each ofthe through-holes 26 c 1 and 26 c 2, wherein the position-settingprotrusion 26 f protrudes from the top face 26 b of the lighting unitbracket 26. The position-setting protrusion 26 f is used to set thefirst optical unit 30 at a correct position in the Y direction.

If the precision of positioning is to be enhanced in the Y directionwithout providing the position-setting protrusion 26 f, the flatness ofthe entire top face of the lighting unit bracket 26 is required to beenhanced, which is costly. By providing the position-setting protrusion26 f, the flatness is required to be enhanced only at theposition-setting protrusion 26 f. Therefore, the precision ofpositioning can be enhanced in the Y direction while reducing the cost.

Further, the top face of the lighting unit bracket 26 has an openingcovered by a light shield plate 262 engaging the lower end of theprojection lens unit 31, by which the intrusion of light from the upperside into the casing 261 can be prevented.

Further, the top face 26 b of the lighting unit bracket 26 has a cutoutbetween the through-holes 26 c 1 and 26 c 2 of the top face 26 b so thatthe second optical unit 40 can be screwed to the first optical unit 30easily, to be described later.

A light source positioning member 26 a 3 is disposed at one end of thelighting unit bracket 26 at the color wheel 21 side (Z direction in FIG.6). The light source positioning member 26 a 3 has a cylinder-like shapehaving a through-hole, to which the light source position-setting member64 a 3 having the protruded-shape (FIG. 4), disposed at the top face ofthe holder 64 of the light source unit 60, engages. Further, two lightsource positioning members 26 a 1 and 26 a 2 having protruded-shape aredisposed at a lower side of the light source positioning member 26 a 3,to which the light source position-setting member 64 a 1 and 64 a 2disposed on the holder 64 at the light-source bracket 62 side, which arethrough-holes, engage respectively. By respectively engaging the lightsource position-setting members 64 a 1 to 64 a 3 disposed for the holder64 to the light source positioning members 26 a 1 to 26 a 3 disposed forthe lighting unit bracket 26 of the lighting unit 20, the light sourceunit 60 can be fixed at the correct position of the lighting unit 20(FIG. 3).

Further, the lighting unit bracket 26 includes a lighting unit cover 28that covers the color wheel 21 and the light tunnel 22.

FIG. 7 shows a light path L of light in the lighting unit 20. The colorwheel 21 has a disc shape and is fixed on a motor shaft of a color motor21 a. The color wheel 21 includes, for example, R (red), G (green), andB (blue) filters along the rotation direction. The light focused by areflector disposed for the holder 64 of the light source unit 60 passesthrough the light exiting window 63, and then reaches the peripheralarea of the color wheel 21. The light that has reached the peripheralarea of the color wheel 21 is separated into R, G, B lights along thetimeline as the color wheel 21 rotates.

The lights separated by the color wheel 21 enter the light tunnel 22.The light tunnel 22 is a tube-shaped member having a square-like crossshape, and its internal face is finished as a mirror face. The lightentered the light tunnel 22 reflects a plurality of times on theinternal face of the light tunnel 22, and is then emitted as uniformlight to the relay lenses 23.

The light that has passed the light tunnel 22 passes the two relaylenses 23, reflects on the cylinder mirror 24 and the concave mirror 25,and is then focused on an image generation face of the DMD 12 as animage.

A description is given of the image generation unit 10 with reference toFIG. 8, which shows a perspective view of the image generation unit 10.As shown in FIG. 8, the image generation unit 10 includes, for example,a DMD board 11 to which the DMD 12 is attached. The DMD 12 is attachedto a socket 11 a disposed on the DMD board 11 while orienting an imagegeneration face composed of micro mirrors arranged in a lattice patternto an upward direction. The DMD board 11 includes a drive circuit todrive micro mirrors.

A heat exchanger such as the heat sink 13 is fixed on a distal side ofthe DMD board 11 (i.e., a face opposite a face having the socket 11 a)to cool the DMD 12. The DMD board 11 has a through-hole area to whichthe DMD 12 is attached, and the heat sink 13 has a protruded portion 13a (FIG. 7) insertable into the through-hole area. The protruded portion13 a has an edge portion having a flat shape. By inserting the protrudedportion 13 a into the through-hole area, the flat edge portion of theprotruded portion 13 a can contact the distal side of the DMD 12 (i.e.,face opposite the image generation face). An elastic and flexible heatconduction sheet can be attached on the flat edge portion of theprotruded portion 13 a and/or an area of the distal side of the DMD 12so that the heat sink 13 and the distal side of the DMD 12 can beclosely contacted to enhance the thermal conductivity.

The heat sink 13 can be fixed on a face opposite a face disposed of thesocket 11 a of the DMD board 11 by applying pressure using a fixingdevice 14. The fixing device 14 includes, for example, a plate-likefixing part 14 a at a right distal side of the DMD board 11 (right sidein FIG. 8), and a plate-like fixing part 14 a at a left distal side ofthe DMD board 11 (left side in FIG. 8) disposed at as counterpartmembers with each other. As shown in FIG. 8, one end and other end ofthe plate-like fixing parts 14 a are linked by a pressure member 14 bextending in the Z direction in FIG. 8.

When the image generation unit 10 is fixed to the lighting unit bracket26 (FIG. 6) using screws, the heat sink 13 is pressed and fixed to theface opposite the face disposed of the socket 11 a of the DMD board 11by applying force from the fixing device 14.

A description is given of fixing of the lighting unit bracket 26 of theimage generation unit 10. Initially, the image generation unit 10 ispositioned with respect to the lighting unit bracket 26 so that the DMD12 can face the through-hole 26 d disposed on the bottom face of thelighting unit bracket 26 of the lighting unit 20 (FIG. 5). Then, a screwis inserted into each of through-holes disposed for the fixing part 14a, and each of through-holes 15 disposed for the DMD board 11 from alower side, and the screw is screwed into each of screw holes disposedat the bottom face of the screw stopper 262 (FIG. 3) of the lightingunit bracket 26 to fix the image generation unit 10 to the lighting unitbracket 26. Further, as the screw is screwed into the screw stopper 262disposed for the lighting unit bracket 26, the pressure member 14 bpresses the heat sink 13 toward the DMD board 11. With such aconfiguration, the heat sink 13 can be pressed and fixed on the faceopposite the face disposed with the socket 11 a of the DMD board 11 byusing the fixing device 14.

As such, the image generation unit 10 can be fixed to the lighting unitbracket 26, and the three legs 29 shown in FIG. 5 can support the weightof the image generation unit 10.

The image generation face of the DMD 12 is composed of a plurality ofmovable micro mirrors arranged in a lattice pattern. Each of micromirrors can incline the mirror face about a torsion shaft for a givenangle, and can be set with two conditions of “ON” and “OFF”. When themicro mirror is set “ON,” the light coming from the light source 61 isreflected toward the first optical system 70 (FIG. 2) as shown by anarrow L2 shown in FIG. 7. When the micro mirror is set “OFF,” the lightcoming from the light source 61 is reflected toward the OFF plate 27,retained on the side face of the lighting unit bracket 26 shown in FIG.6, as shown by an arrow L1 shown in FIG. 7. Therefore, by driving eachmirror independently, the light projection can be controlled for eachpixel of image data to generate an image.

The light reflected to the OFF plate 27 is absorbed as heat and then theOFF plate 27 is cooled by the airflow flowing outside of the OFF plate27.

A description is given of the first optical unit 30 with reference toFIG. 9, which shows a perspective view of the first optical unit 30 withthe lighting unit 20 and the image generation unit 10. As shown in FIG.9, the first optical unit 30 is disposed over the lighting unit 20, andincludes, for example, the projection lens unit 31, and the lens holder32. The projection lens unit 31 retains the first optical system 70(FIG. 2) composed of a plurality of lenses, and the lens holder 32retains the projection lens unit 31. The lens holder 32 is disposed withfour legs 32 a 1 to 32 a 4 extending toward the downside, wherein FIG. 9shows the legs 32 a 2 and 32 a 3. The leg 32 a 1 is shown in FIG. 3, andthe leg 32 a 4 is shown in FIG. 5. Each of the legs 32 a 1 to 32 a 4 isformed of a screw hole on its bottom face to be used when fixed with thelighting unit bracket 26 using a screw.

Further, the projection lens unit 31 is disposed with a focus gear 36meshed with an idler gear 35. The idler gear 35 is meshed with a levergear 34, and the focus lever 33 is fixed to a rotation shaft of thelever gear 34. As shown in FIG. 1, the end of the focus lever 33 isexposed outside of the projector 1.

When the focus lever 33 is operated, the focus gear 36 is rotated viathe lever gear 34 and the idler gear 35. When the focus gear 36 isrotated, each of the plurality of lenses composing the first opticalsystem 70 disposed in the projection lens unit 31 can be moved to agiven direction to adjust a focus point of a projection image.

Further, the lens holder 32 includes, for example, four threadedthrough-holes 32 c 1 to 32 c 3 so that the second optical unit 40 can befixed with the first optical unit 30 using screws, in which a screw 48is screwed into each of the threaded through-holes 32 c 1 to 32 c 3.FIG. 9 shows three threaded through-holes 32 c 1 to 32 c 3, and thescrew 48 is inserted into each of the threaded through-holes 32 c 1 to32 c 3. In FIG. 9, the end of the screw 48 is shown. Further,positioning protruded members 32 d 1 to 32 d 3 are respectively formedaround each of the threaded through-holes 32 c 1 to 32 c 3, in whicheach of the positioning protruded members 32 d 1 to 32 d 3 protrudesfrom the face of the lens holder 32. FIG. 9 shows the positioningprotruded members 32 d 1 to 32 d 3.

FIG. 10 shows a cross-sectional view along a line D-D of FIG. 9. Asshown in FIG. 10, each of the legs 32 a 1 and 32 a 2 is disposed withpositioning protruded members 32 b 1 and 32 b 2, respectively. Thepositioning protruded member 32 b 1 (right side in FIG. 10) is insertedin the position-setting hole 26 e 1 having the circular hole shape,which is the primary position-setting hole disposed on the top face 26 bof the lighting unit bracket 26. The positioning protruded member 32 b 2(left side in FIG. 10) is inserted in the position-setting hole 26 e 2having the slot hole shape, which is the secondary position-settinghole. With such a configuration, the position in the Z direction and Xdirection can be set correctly.

Further, a screw 37 is inserted into each of the through-holes 26 c 1 to26 c 4 disposed for the top face 26 b of the lighting unit bracket 26,and then screwed into screw holes of each of the legs 32 a 1 to 32 a 4of the lens holder 32, by which the first optical unit 30 can be fixedto the lighting unit 20 with a correct position.

The second optical unit 40 includes a mirror holder 45 (FIG. 12) thatcovers a portion of the projection lens unit 31 above the lens holder 32to be described later. Further, as shown in FIG. 3, a space between apart of the lens holder 32, lower than a part of the lens holder 32corresponding to the projection lens unit 31 and the top face 26 b ofthe lighting unit bracket 26 of the lighting unit 20 is exposed outside.However, because the projection lens unit 31 engages the lens holder 32,the light does not enter the light path of projection light from suchexposed part.

A description is given of the second optical unit 40 with reference toFIG. 11 and FIG. 12. FIG. 11 shows a perspective view of the secondoptical unit 40 used as a second optical system configured with theprojection lens unit 31, the lighting unit 20, and the image generationunit 10. As shown in FIG. 11, the second optical unit 40 includes, forexample, the reflection mirror 41, and the curved mirror 42 having theconcave shape. The reflection face of the curved mirror 42 can befinished as a circular face, a rotation symmetrical non-circular face, afree curve shape, or the like.

FIG. 12 shows a perspective view of the second optical unit 40 with thefirst optical unit 30, the lighting unit 20, and the image generationunit 10. The second optical unit 40 passes the light reflected from thecurved mirror 42, and includes the transparent glass 51 to preventintrusion of dust to optical parts in the projector 1.

The second optical unit 40 includes, for example, a mirror bracket 43, afree mirror bracket 44, and a mirror holder 45. The mirror bracket 43retains the reflection mirror 41 and the transparent glass 51. The freemirror bracket 44 retains the curved mirror 42. The mirror holder 45holds the mirror bracket 43 and the free mirror bracket 44.

The mirror holder 45 has a box-like shape while the upper side, lowerside, and one side such as right side in the X direction in FIG. 12 areopened, and thereby the mirror holder 45 has a U-like shape when viewedfrom the top. The upper part of the mirror holder 45 includes aninclined portion extending along a direction set between the middle ofthe X and Y directions by increasing the height, and includes a parallelface parallel to the X direction. The inclined portion is disposed at aproximal side of the parallel face in the X direction. Further, theperipheral side of upper opening of the mirror holder 45 disposed at aproximal side in the X direction and extending in the Z direction isparallel to the Z direction in FIG. 12.

The mirror bracket 43 is attached to the upper part of the mirror holder45. The mirror bracket 43 includes an inclined side 43 a and ahorizontal side 43 b. The inclined side 43 a rises along a direction setbetween the middle of the X and Y directions by increasing the height asshown in FIG. 12. The horizontal side 43 b extends in a directionparallel to the X direction in FIG. 12. The inclined side 43 a contactsthe peripherals of the inclined portion of the mirror holder 45, and thehorizontal side 43 b contacts the peripherals of the horizontal part ofthe mirror holder 45, which is the top of the mirror holder 45. Theinclined side 43 a includes an opening, and the reflection mirror 41 isretained to cover the opening of the inclined side 43 a. The horizontalside 43 b includes an opening, and the transparent glass 51 is retainedto cover the opening of the horizontal side 43 b.

Each end of the reflection mirror 41 in the Z direction is pressed tothe inclined side 43 a of the mirror bracket 43 by the mirror pressingmember 46 such as a leaf spring to hold the reflection mirror 41 at theinclined side 43 a of the mirror bracket 43. For example, as shown inFIG. 12, one end of the reflection mirror 41 in the Z direction is fixedby the two mirror pressing members 46, and other end of the reflectionmirror 41 in the Z direction is fixed by the one mirror pressing member46.

Each end of the transparent glass 51 in the Z direction is pressed tothe horizontal side 43 b of the mirror bracket 43 by a glass pressingmember 47 such as a leaf spring to hold the transparent glass 51 on themirror bracket 43. Each end of the transparent glass 51 in the Zdirection is retained by using one glass pressing member 47 at each endin the Z direction.

The free mirror bracket 44 to retain the curved mirror 42 includes anarm portion 44 a at each side of the free mirror bracket 44, in whichthe arm portion 44 a extends and inclines along a direction set betweenthe middle of the X and Y directions as shown in FIG. 12. Further, thefree mirror bracket 44 includes a link portion 44 b that links such twoarm portions 44 a at the upper portion of the arm portions 44 a. The armportion 44 a of the free mirror bracket 44 is attached to the mirrorholder 45 so that the curved mirror 42 covers an opening of the mirrorholder 45.

The curved mirror 42 pressed toward the link portion 44 b of the freemirror bracket 44 by a free mirror pressing member 49 such as a leafspring at a substantially center of one end side of the transparentglass 51. Further, each end side of the first optical system 70 in the Zdirection in FIG. 12 is fixed to the arm portion 44 a of the free mirrorbracket 44 using a screw.

The second optical unit 40 is stacked and fixed on the lens holder 32 ofthe first optical unit 30. Specifically, the bottom side of the mirrorholder 45 has a bottom face 451 that faces an upper face of the lensholder 32. The bottom face 451 has three screw stoppers 45 a 1 to 45 a 3having tube-like shape, which can be fixed with the first optical unit30 by screws. FIG. 12 shows the screw stoppers 45 a 1 and 45 a 2, andFIG. 5 shows the screw stopper 45 a 3. The second optical unit 40 isfixed to the first optical unit 30 using screws, in which the screw 48is inserted into each of the threaded through-holes 32 c 1 to 32 c 3provided for the lens holder 32 of the first optical unit 30, andscrewed into each of the screw stoppers 45 a 1 to 45 a 3 to fix thesecond optical unit 40 to the first optical unit 30.

In such a configuration, the bottom face of the mirror holder 45 of thesecond optical unit 40 contacts the positioning protruded members 32 d 1to 32 d 3 of the lens holder 32, by which the second optical unit 40 canbe fixed at a correct position in Y direction.

As shown in FIG. 12, when the second optical unit 40 is stacked andfixed on the lens holder 32 of the first optical unit 30, a portion ofthe projection lens unit 31 that is above the lens holder 32 is encasedin the mirror holder 45 of the second optical unit 40. Further, when thesecond optical unit 40 is stacked and fixed on the lens holder 32, aspace is set between the curved mirror 42 and the lens holder 32, andthe idler gear 35 (FIG. 9) may be set in such space.

FIG. 13 shows a schematic view of the light path from the first opticalsystem 70 to the projection plane 101 such as a screen. The light fluxthat has passed through the projection lens unit 31 configuring thefirst optical system 70 is used to generate an intermediate imagebetween the reflection mirror 41 and the curved mirror 42, which is aconjugate image with respect to an image generated by the DMD 12. Suchintermediate image is generated as a curved image between the reflectionmirror 41 and the curved mirror 42. Such intermediate image enters thecurved mirror 42 having a concave shape, and the curved mirror 42enlarges the intermediate image and projects the enlarged image onto theprojection plane 101.

As such, an optical projection system can be configured with the firstoptical system 70, and the second optical system. In such aconfiguration, the intermediate image is generated between the firstoptical system 70 and the curved mirror 42 of the second optical system,and the intermediate image is enlarged and projected by the curvedmirror 42, by which the projection distance to the screen can be setshorter. Therefore, the projector 1 can be used in small meeting roomsor the like.

Further, as shown in FIG. 13, the first optical unit 30 and the secondoptical unit 40 are stacked and fixed to the lighting unit bracket 26.Further, the image generation unit 10 is fixed to the lighting unitbracket 26. Therefore, the legs 29 of the lighting unit bracket 26 canbe fixed to the base member 53 while supporting the weight of the firstoptical unit 30, the second optical unit 40, and the image generationunit 10.

FIG. 14 schematically shows a layout of units in the projector 1. Asshown in FIG. 14, the image generation unit 10, the lighting unit 20,the first optical unit 30, and the second optical unit 40 are stackedalong the Y direction, which is the short side direction of theprojection plane 101. As shown in FIG. 14, the light source unit 60 isarranged in the Z direction with respect to other stacked units composedof the image generation unit 10, the lighting unit 20, the first opticalunit 30, and the second optical unit 40, which is the long sidedirection of the projection plane 101. As such, in an exampleembodiment, the image generation unit 10, the lighting unit 20, thefirst optical unit 30, the second optical unit 40, and the light sourceunit 60 can be arranged along the Y direction and Z directions, whichare parallel to a projection image and the projection plane 101.

Specifically, a projection optical system B having the first opticalunit 30 and the second optical unit 40 is stacked on the image generatorA having the image generation unit 10 and the lighting unit 20. Thelight source unit 60 is coupled to the image generator A in a directionperpendicular to the stacking direction of the image generator A and theprojection optical system B. Further, the image generator A and thelight source unit 60 can be arranged along a direction parallel to thebase member 53. Further, the image generator A and the projectionoptical system B may be arranged along a direction perpendicular to thebase member 53, in which the image generator A is disposed over the basemember 53, and then the projection optical system B is disposed over theimage generator A.

Further, as shown in FIG. 14, a power source unit 80 is stacked ordisposed above the light source unit 60, wherein the power source unit80 supplies power to the light source 61 and the DMD board 11. The lightsource unit 60, the power source unit 80, the image generator A, and theprojection optical system B are encased in a casing of the projector 1.The casing of the projector 1 includes the top face of the projector 1,the base member 53, and an outer cover 59 (FIG. 18) used as the sideface of the projector 1 to be described later.

FIG. 15 shows an example of use environment of the projector 1 accordingto an example embodiment, and FIGS. 16 and 17 show examples of useenvironment of conventional projectors 1A and 1B. As shown in FIG. 15 toFIG. 17, when the projector is used in a meeting room, the projector maybe placed on a table 100, and images are projected on the projectionplane 101 such as a white board.

As shown in FIG. 16, as for the conventional projector 1A, the DMD 12,the lighting unit 20, the first optical system 70, and the secondoptical system such as the curved mirror 42 are serially arranged alongin the direction perpendicular to the projection plane 101 to which aprojection image is projected. Therefore, the length of the projector 1Ain the direction perpendicular to the projection plane 101 (i.e., Xdirection) becomes longer, and thereby a greater space is required forthe projector 1A in the direction perpendicular to the projection plane101.

Typically, chairs that participants sit and desks that participants usemay be arranged in the direction perpendicular to the projection plane101 when to see images projected on the projection plane 101. Therefore,if a greater space for the projector 1A is required in the directionperpendicular to the projection plane 101, the arrangement space forchairs and the arrangement space for desks are restricted and therebynot convenient when the projector is used.

As shown in FIG. 17, as for the conventional projector 1B, the DMD 12,the lighting unit 20, and the first optical system 70 are seriallyarranged along in a direction parallel to the projection plane 101 towhich a projection image is projected. Therefore, compared to theprojector 1A shown in FIG. 16, the length of the projector 1B in thedirection perpendicular to the projection plane 101 can be set shorter.However, as for the projector 1B of FIG. 17, the light source 61 isarranged in the direction perpendicular to the projection plane 101 andis arranged after the lighting unit 20 in the direction perpendicular tothe projection plane 101, and thereby the length of the projector 1B inthe direction perpendicular to the projection plane 101 may not beeffectively set shorter.

As for the projector 1 of an example embodiment shown in FIG. 15, theimage generator A having the image generation unit 10 and the lightingunit 20, and the projection optical system B having the first opticalunit 30 and the reflection mirror 41 are serially arranged along in adirection parallel to the projection plane 101, to which a projectionimage is projected. In such a configuration, the image generator A andthe projection optical system B are serially arranged along in adirection parallel to the Y direction in FIG. 15. Further, the lightsource unit 60 and the lighting unit 20 are serially arranged along in adirection parallel to the projection plane 101, which means the lightsource unit 60 and the lighting unit 20 are serially arranged along theZ direction in FIG. 15.

As such, as for the projector 1 according to an example embodiment, thelight source unit 60, the image generation unit 10, the lighting unit20, the first optical unit 30, and the reflection mirror 41 can bearranged in a direction parallel to the projection plane 101 such as theZ direction or Y direction in FIG. 15. As such, the light source unit60, the image generation unit 10, the lighting unit 20, the firstoptical unit 30, and the reflection mirror 41 can be arranged in adirection parallel to the projection plane 101 such as the Z directionor Y direction in FIG. 15. Therefore, the length of the projector 1 inthe direction perpendicular to the projection plane 101 (i.e., Xdirection in FIG. 15) can be set shorter than the length of theprojectors 1A and 1B shown in FIG. 16 and FIG. 17.

With such a configuration, the projector 1 may not cause problems whenarranging a space for chairs and desks, by which the projector 1 havinga good enough level of convenience can be devised.

Further, as shown in FIG. 14, the power source unit 80 is stacked ordisposed above the light source unit 60 to supply power to the lightsource 61 and the DMD board 11, by which the length of the projector 1in the Z direction can be set shorter.

FIG. 18 shows another example use of the projector 1 according to anexample embodiment. As shown in FIG. 18, the projector 1 can be fixed ona ceiling 105. Because the projector 1 has a short side in the directionperpendicular to the projection plane 101, the projector 1 can be fixedon the ceiling 105 without interfering a lighting device 106 disposed onthe ceiling 105.

Further, although the second optical system may be configured with thereflection mirror 41 and the curved mirror 42, but the second opticalsystem can be configured with only the curved mirror 42. Further, thereflection mirror 41 can be a plane mirror, a mirror having a positiverefractive power, and a mirror having a negative refractive power.Further, the curved mirror 42 may be a concave mirror or a convexmirror. When the curved mirror 42 is a convex mirror, the first opticalsystem 70 is configured in a way so that no intermediate image isgenerated between the first optical system 70 and the curved mirror 42.

Because the light source 61 has a lifetime for effective use, the lightsource 61 is required to be replaced with a new one periodically.Therefore, the light source unit 60 is detachably attached to a body ofthe projector 1.

FIG. 19 shows a perspective view of the projector 1 viewed from a bottomface of the projector 1, wherein the bottom face may be placed on atable. As shown in FIG. 19, the bottom face of the projector 1 includesthe base member 53 and the openably closable cover 54. The openablyclosable cover 54 includes a rotate-able member 54 a. When therotate-able member 54 a is rotated, the openably closable cover 54 isunlocked from the body of the projector 1, by which the openablyclosable cover 54 can be removed from the body of the projector 1.Further, the base member 53 includes, for example, a power-source airintake port 56 at a position next to the openably closable cover 54 inthe X direction.

Further, as shown in FIG. 19, an air-intake port 84 and the input unit88 are disposed on one Y-X plane of the outer cover 59 of the projector1. The input unit 88 is used to input image data from externalapparatuses such as personal computers.

FIG. 20 shows a perspective view of the projector 1 when the openablyclosable cover 54 is removed from the projector 1. When the openablyclosable cover 54 is removed, the light-source bracket 62 of the lightsource unit 60 is exposed, wherein the exposed side is the opposite sidethat the light source 61 is attached. The light-source bracket 62includes a knob 66, which is pivotable about the pivot center O1indicated by a dotted line in FIG. 20.

When removing the light source unit 60 from the body of the projector 1,the knob 66 is pivoted and opened by picking the knob 66, by which thelight source unit 60 can be removed from an opening of the body of theprojector 1. When attaching the light source unit 60 into the body ofthe projector 1, the light source unit 60 is inserted into the body ofthe projector 1 through the opening. When the light source unit 60 isinserted into the body of the projector 1, the connector 62 a (FIG. 4)is connected with a power-source connector in the body of the projector1, and the three light source position-setting members 64 a 1 to 64 a 3of the holder 64 (FIG. 4) engage with three light source positioningmembers 26 a 1 to 26 a 3 (FIG. 6) disposed for the lighting unit bracket26 of the lighting unit 20, by which the light source unit 60 is set ata correct position in the body of the projector 1, and the attachment ofthe light source unit 60 completes. Then, the openably closable cover 54is attached to the base member 53.

As such, the knob 66 is provided for the light source unit 60, but thepass-through area 65 shown in FIG. 20, which protrudes to the openablyclosable cover 54 can be used as a knob. The pass-through area 65 may bealso referred to as the duct 65.

Further, the base member 53 is disposed with three legs 55. By rotatingthe legs 55, the protruded length of the legs 5 from the base member 53can be changed, by which the height adjustment in the Y direction of theprojector 1 can be conducted.

Further, as shown in FIG. 20, an exhaust port 85 is disposed at otherY-X plane of the outer cover 59.

FIG. 21 shows a schematic view of airflow in the projector 1 accordingto an example embodiment. FIG. 21 shows the projector 1 viewed from theX direction, wherein the X direction is perpendicular to the projectionplane 101. FIG. 22 shows a cross-sectional view of an internalconfiguration of the projector 1 corresponding to the view of FIG. 21.The arrows shown in FIG. 21 and FIG. 22 indicate directions of airflow.FIG. 23 shows a cross-sectional view of the projector 1 cut at line E-Ein FIG. 22.

As shown in FIG. 21, the projector 1 includes the air-intake port 84disposed its one face (left side in FIG. 21), and the exhaust port 85disposed its other face (right side in FIG. 21). The air-intake port 84has an opening to intake external air into the projector 1. The exhaustport 85 has an opening to exhaust air from the projector 1. Further, anexhaust fan 86 is disposed at a position facing the exhaust port 85.

When the projector 1 is viewed from the X direction, which is adirection perpendicular to the projection plane 101, a part of theexhaust port 85 and a part of the air-intake port 84 may be disposedbetween the light source unit 60 and the operation unit 83. Further, aflow path is set between a rear face of the curved mirror 42 and theouter cover 59 facing the rear face of the curved mirror 42 so that aircan flow in such space.

With such a configuration, the external air taken from the air-intakeport 84 can flow through along the Z-Y plane of the mirror holder 45 ofthe second optical unit 40 (FIG. 12), and the rear face of the curvedmirror 42 by following the mirror holder 45 and curving of the rear faceof the curved mirror 42, and then flow to the exhaust port 85.

Further, the curved mirror 42 is a concave-shaped mirror having thepositive refractive power as above mentioned, and thereby the rear faceof the curved mirror 42 has a convex shape.

Further, the power source unit 80 has a configuration having threesides. Therefore, when the power source unit 80 disposed over the lightsource unit 60 is viewed from the Z direction in FIG. 21, the powersource unit 80 can be viewed as a U-shape configuration without a sidefacing the light source unit 60. Further, the external air taken fromthe air-intake port 84 flows along the mirror holder 45 and the curvingof the rear face of the curved mirror 42 toward the exhaust port 85, andthen further flows to a space encircled by the power source unit 80having the three sides, and is then exhausted from the exhaust port 85.

As such, the part of the exhaust port 85 and the air-intake port 84 aredisposed between the light source unit 60 and the operation unit 83 whenthe projector 1 is viewed from the X direction, which is a directionperpendicular to the projection plane 101. In such a configuration, anairflow passing through a space between the light source unit 60 and theoperation unit 83 and exhausted from the exhaust port 85 can begenerated.

Further, a light source blower 95 is disposed at a position that cansuck air around the color motor 21 a (FIG. 5) that drives the colorwheel 21 in the lighting unit 20. With such a configuration, the colormotor 21 a and the light tunnel 22 can be cooled using the airflowgenerated by the air sucking effect of the light source blower 95.

The air sucked in by the light source blower 95 passes a light sourceduct 96, and then flows into a light-source air supply port 64 b (FIG.4) of the holder 64. Further, a part of the air flowing into the lightsource duct 96 flows into a space between a light source housing 97 andthe outer cover 59 from an opening 96 a formed on a face of the lightsource duct 96 opposing the outer cover 59 (FIG. 19).

The air flowing into the space between the light source housing 97 andthe outer cover 59 from the opening 96 a of the light source duct 96cools the light source housing 97 and the outer cover 59, and is thenexhausted from the exhaust port 85 using the exhaust fan 86, which willbe described later.

Further, the air flowing to the light-source air supply port 64 b flowsinto the light source 61 to cool the light source 61, and is thenexhausted from the light-source air exhaust port 64 c disposed on thetop face of the holder 64. The air exhausted from the light-source airexhaust port 64 c is then exhausted from an opening formed on the topface of the light source housing 97 toward the exhaust port 85 along afluid guide 87 as shown in FIG. 22. Then, the air exhausted from thelight source housing 97 (i.e., high-temperature air) is mixed withexternal air (i.e., low-temperature air) that flows around the secondoptical unit 40 and then flows into the space encircled by the powersource unit 80, and then the mixed air is exhausted from the exhaustport 85 using the exhaust fan 86. As such, the high-temperature airexhausted from the light-source air exhaust port 64 c is mixed with theexternal air (i.e., low-temperature air), and then exhausted from theexhaust port 85. Therefore, the temperature of air exhausted from theexhaust port 85 can be decreased to a lower temperature.

Further, the fluid guide 87 can be omitted from the configuration. Forexample, even without the fluid guide 87, the high temperature airexhausted from the light-source air exhaust port 64 c can be exhaustedfrom the exhaust port 85 because the high temperature air can be mixedwith low-temperature air flowing from the air-intake port 84 toward theexhaust port 85, which flows along the rear face of the curved mirror42, at a space surrounded by a power factor correction (PFC) main powersource board 80 a and a PFC sub-power source board 80 a, to be describedlater.

However, by disposing the fluid guide 87, a direct hit of hightemperature air exhausted from the light-source air exhaust port 64 c tothe PFC main power source board 80 a and the PFC sub-power source board80 a can be prevented.

However, if the fluid guide 87 blocks the entire flow of hightemperature air exhausted from the light-source air exhaust port 64 ctoward the PFC main power source board 80 and the PFC sub-power sourceboard 80 a, the high temperature air may not be mixed with thelow-temperature air flowing along the rear face of the curved mirror 42,by which the high temperature air is exhausted from the exhaust port 85without decreasing its high temperature air, thereby the exhaust port 85becomes high temperature.

Therefore, it is preferable that the air exhausted from the light-sourceair exhaust port 64 c and passing the fluid guide 87 passes the spacesurrounded by the PFC main power source board 80 a and the PFC sub-powersource board 80 a, by which the air exhausted from the light-source airexhaust port 64 c can be mixed with the low-temperature air flowing fromthe air-intake port 84 toward the exhaust port 85, and then the air isexhausted from the exhaust port 85 by decreasing its high temperature,which is safer for a user.

Further, the operation unit 83 is preferably disposed on a top face ofthe projector 1 so that the user can operate the operation unit 83easily. Because the projector 1 includes the transparent glass 51 on itstop face for projecting images on the projection plane 101, theoperation unit 83 may be disposed on a position corresponding to thelight source 61 when viewing the projector 1 from the Y direction.

As such, the low-temperature air, flowing through a space between thelight source unit 60 and the operation unit 83 from the air-intake port84 toward the exhaust port 85, can be used to cool the high-temperatureair, which has become high temperature when the air has cooled the lightsource 61, by which the low-temperature air and high-temperature airbecome mixed air. Such mixed air is then exhausted from the exhaust port85, and thereby the movement of high temperature air to the operationunit 83 can be prevented.

With such a configuration, the temperature increase of the operationunit 83, which may be caused by the high temperature air coming from thelight source 61, can be prevented. Further, a part of air, flowing fromthe air-intake port 84 to the exhaust port 85, flows around the secondoptical unit 40 and then under the operation unit 83 to cool theoperation unit 83. Therefore, the temperature increase of the operationunit 83 can be prevented.

Further, when the exhaust fan 86 sucks in air, external air can besucked from the power-source air intake port 56 disposed on the basemember 53 (FIG. 19). A ballast board to supply power or current to thelight source 61 is disposed at a position distal of the light sourcehousing 97 in the X direction of FIG. 21. The external air sucked fromthe power-source air intake port 56 can flow through a space between thelight source housing 97 and the ballast board in the upward direction tocool the ballast board. Then, the air flows to a space encircled by thepower source unit 80 disposed over the ballast board, and is thenexhausted from the exhaust port 85 using the exhaust fan 86.

In an example embodiment, a fan to generate the airflow from theair-intake port 84 to the exhaust port 85 is disposed at an exhaustside, in which the exhaust fan 86 is used as such fan. If the fan isprovided at the exhaust side, the air supply volume from the air-intakeport 84 into the projector 1 can be set greater than a fan disposed nearthe air-intake port 84.

If the fan is disposed near the air-intake port 84, the flow rate ofexternal air supplied into the projector 1 may be decreased because thesecond optical unit 40 exists in a direction that the fan supplies air.

In contrast, if the fan (e.g., exhaust fan 86) is disposed near theexhaust port 85, the flow rate exhausted from the exhaust fan 86 may notdecrease because objects may not exist outside the exhaust port 85.Therefore, when a given volume of air is exhausted from the exhaust fan86, the same volume of air can be taken from the air-intake port 84, bywhich the air volume supplied from the air-intake port 84 into theprojector 1 may not decrease. Therefore, the air can flow from theair-intake port 84 toward the exhaust port 85 at a given wind pressure,by which hot air rising from the light source 61 can effectively flow tothe exhaust port 85 using the air flow flowing from the air-intake port84 toward the exhaust port 85.

Further, a cooling unit 120 to cool the heat sink 13 of the imagegeneration unit 10 and the light-source bracket 62 of the light sourceunit 60 is disposed at the lower left side of the projector 1 as shownin FIG. 21. The cooling unit 120 includes, for example, an air-intakeblower 91, a vertical duct 92 disposed under the air-intake blower 91,and a horizontal duct 93 connected at the bottom of the vertical duct92.

The air-intake blower 91 is disposed at a lower side of the air-intakeport 84 while facing the air-intake port 84. The air-intake blower 91sucks external air from the air-intake port 84 via a side face of theair-intake blower 91 facing the air-intake port 84, and also sucks airfrom the body of the projector 1 from another side, opposite the sideface of the air-intake blower 91 facing the air-intake port 84. Suchsucked airflows in the vertical duct 92 disposed under the air-intakeblower 91. The air flowing into the vertical duct 92 flows downward, andthen flows to the horizontal duct 93 connected at the bottom of thevertical duct 92.

As shown in FIG. 21, the heat sink 13 is present in the horizontal duct93. Therefore, the heat sink 13 can be cooled by the air flowing in thehorizontal duct 93. By cooling the heat sink 13, the DMD 12 can becooled effectively and efficiently, by which high temperature of the DMD12 can be prevented.

The air flowing through the horizontal duct 93 flows into thepass-through area 65 (duct 65) or the opening 65 a disposed for thelight-source bracket 62 of the light source unit 60 (FIG. 4). The airflowing into the opening 65 a flows through a space between the openablyclosable cover 54 and the light-source bracket 62, and cools theopenably closable cover 54.

Meanwhile, the air flowing into the pass-through area 65 cools thelight-source bracket 62, and then flows into a space opposite the lightexit side of the light source 61 to cool a face of a reflector 67 (FIG.25) so that the reflector 67 of the light source 61 is cooled, in whichthe face of the reflector 67 cooled by the air is a face opposite thereflection face of the reflector 67. Therefore, the air that passesthrough the pass-through area 65 can take heat from both of thelight-source bracket 62 and the light source 61.

The air, which has passed near the reflector 67, passes through anexhaust duct 94, which is used to guide the air from the top side of thelight-source bracket 62 to the lower side of the exhaust fan 86, andthen converges into the air exhausted from the light-source air exhaustport 64 c, and then flows to the exhaust port 85, and then the air canbe exhausted from the exhaust port 85 using the exhaust fan 86.

Further, the air flowing into a space between the openably closablecover 54 and the light-source bracket 62 through the opening 65 a coolsthe openably closable cover 54, and then flows inside the projector 1,and is then exhausted from the exhaust port 85 using the exhaust fan 86.

The heat generated at the light source 61 heats the light source housing97 used as a housing of the light source 61, by which the light sourcehousing 97 becomes hot. Then, such hot light source housing 97 heats theouter cover 59, which is a side face of the projector 1 facing the lightsource housing 97, by which the temperature of the outer cover 59increases. Specifically, the hot light source housing 97 heats the outercover 59 from an inner side face of the outer cover 59. If thetemperature of the outer cover 59 increases, the outer cover 59 becomeshigh temperature and hot. If a user touches such hot outer cover 59 ofthe projector 1, the user may feel uncomfortable. To prevent suchuncomfortable condition, it is preferable to set the temperature of theouter cover 59 at a given level such as 95 Celcius degrees or less, ormore preferably 75 Celcius degrees or less.

In view of such temperature condition, the light source duct 96 isformed with the opening 96 a as above described so that a part of airsucked by the light source blower 95 can be flowed into a space betweenthe light source housing 97 and the outer cover 59 through the opening96 a. A description is given of the opening 96 a of the light sourceduct 96.

FIG. 24 shows a perspective view of the projector 1 when the outer cover59 is removed. In FIG. 24, the light source blower 95 is disposed infront of the light source housing 97 in the X direction. The lightsource blower 95 is used to suck air in the projector 1 from both sidefaces of light source blower 95. The exhaust port of the light sourceblower 95 is connected to an air intake end of the light source duct 96.The light source duct 96 extends through an opening formed on the lightsource housing 97, and an exhaust end of the light source duct 96 facesthe light-source air supply port 64 b formed on a face of the holder 64of the light source unit 60 encased in the light source housing 97.

FIG. 25 shows a cross-sectional view of the light source housing 97 ofthe projector 1. As shown in FIG. 25, the light source duct 96 isinclined from the light source blower 95 to the light source 61. The airsucked by the light source blower 95 moves in the light source duct 96from left to right in FIG. 25, and then takes a flow path extendingtoward the light source 61, and flows to the light-source air supplyport 64 b.

The opening 96 a of the light source duct 96 is formed on a wall face ofthe light source duct 96, which is one side the flow path of the lightsource duct 96. A part of the air flowing from the light source blower95 straightforwardly hits a wall face of the light source duct 96.Therefore, by providing the opening 96 a on the wall face of the lightsource duct 96, a part of the air flowing in the light source duct 96can be smoothly flowed to a space between the light source housing 97and the outer cover 59 through the opening 96 a. The size and shape ofthe opening 96 a can be changed in view of the flow rate through theopening 96 a. For example, the flow rate through the opening 96 a can beset at one fifth of the flow rate into the light source 61.

The air flowing through the opening 96 a flows in the space between thelight source housing 97 and the outer cover 59 in a direction from leftto right in FIG. 25. After cooling the outer cover 59 and the lightsource housing 97, the air moves upward by the suction power of theexhaust fan 86, and is then exhausted from the exhaust port 85 by usingthe exhaust fan 86.

Meanwhile, the air flowing from the light source duct 96 to the lightsource 61 via the light-source air supply port 64 b cools the lightsource 61 as above described, and then passes through the light-sourceair exhaust port 64 c and the opening formed on the top face of thelight source housing 97, and then moves the upward direction from thelight source housing 97. Further, such air is mixed with low-temperatureair, taken from the upper part of the air-intake port 84 using theexhaust fan 86, and then the mixed air is exhausted from the exhaustport 85 by using the exhaust fan 86.

As such, the light source housing 97 can be cooled by the air flowingthrough the space between the outer cover 59 and the light sourcehousing 97. With such a configuration, the temperature increase of theouter cover 59, which may be caused by heat of the light source housing97, can be suppressed, and the outer cover 59 can be cooled. Therefore,the temperature increase of the outer cover 59 can be effectivelysuppressed. With such a configuration, even if a user touches such outercover 59, facing the light source housing 97, the user may not feeluncomfortable. In contrast, if the temperature of the outer cover 59 istoo high, the user may feel uncomfortable.

Further, by cooling the light source housing 97, the temperatureincrease of the light source 61 can be suppressed, and the light source61 can be cooled effectively.

The above-described image projection apparatus such as the projector 1that projects an image on a projection plane may have following effects.The projector 1 includes the light source 61, and a ventilation unitsuch as the light source blower 95 to send air to the light source 61.The projector 1 includes the flow path, which is a space between thelight source housing 97 and the side face of the projector 1 (e.g.,outer cover 59). A part of air, being supplied to the light source 61 byusing the ventilation unit, can pass the flow path. In the projector 1,the light source housing 97 encases the light source 61 in the projector1. With such a configuration, the light source housing 97 can be cooled,and the temperature increase of the outer cover 59 caused by the heat ofthe light source housing 97 can be suppressed. Because the outer cover59 can be also cooled, the temperature increase of the outer cover 59can be effectively suppressed. With such a configuration, the outercover 59 facing the light source housing 97 can be prevented frombecoming too hot or high temperature condition.

Further, the projector 1 includes a duct such as the light source duct96 to flow air to the light source 61 from the ventilation unit such asthe light source blower 95. The light source duct 96 is formed with theopening 96 a on its wall face to flow air to the space between the lightsource housing 97 and the side face of the projector 1 (e.g., outercover 59). With such a configuration, a part of air flowing into thelight source duct 96 from the ventilation unit such as the light sourceblower 95 can flow to the space between the light source housing 97 andthe outer cover 59.

In the above described example embodiment, an image projection apparatussuch as the projector 1 can suppress the temperature increase of theside face of the image projection apparatus while suppressing the costand size increase of the apparatus.

In the above described example embodiment, air to be send to the lightsource by using the ventilation unit is partially flowed to a spacebetween the light source housing and the side face of the imageprojection apparatus to cool the side face of the image projectionapparatus and the light source housing. With such a configuration, thetemperature increase of side face of the image projection apparatus canbe suppressed. Further, such partial airflow to the space between thelight source housing and the inner side face of the image projectionapparatus can be supplied using one ventilation unit that supplies airto the light source. Therefore, the cost and size of the imageprojection apparatus can be suppressed compared to a configurationemploying one ventilation unit to send air to the light source andanother ventilation unit to send air to the space between the lightsource housing and the side face of the image projection apparatus.

Numerous additional modifications and variations are possible in lightof the above teachings. It is therefore to be understood that within thescope of the appended claims, the disclosure of the present inventionmay be practiced otherwise than as specifically described herein. Forexample, elements and/or features of different examples and illustrativeembodiments may be combined each other and/or substituted for each otherwithin the scope of this disclosure and appended claims.

What is claimed is:
 1. An image projection apparatus for projecting animage on a projection plane, comprising: a light source; a light sourcehousing to encase the light source; a ventilation unit to send air tothe light source; a flow path set between the light source housing and aside face of the image projection apparatus, wherein a part of the airsent to the light source by using the ventilation unit is directlyflowed into the flow path; and an external cover of the image projectionapparatus, the external cover having the side face, wherein the lightsource housing is provided in the external cover, to define the flowpath between the light source housing and the external cover.
 2. Theimage projection apparatus of claim 1, further comprising a ductconnecting the ventilation unit and the light source housing for flowingair from the ventilation unit to the light source, wherein the duct hasa wall face formed with an opening, through which the part of the airfrom the ventilation unit is flowed to the flow path set between thelight source housing and the side face of the image projectionapparatus.
 3. The image projection apparatus of claim 1, wherein thelight source includes a reflector, and the light source housing housesthe reflector therein.
 4. The image projection apparatus of claim 2,wherein the light source includes a reflector, and the light sourcehousing houses the reflector therein.
 5. The image projection apparatusof claim 2, wherein the wall face of the duct is inclined with respectto the direction of air flow from the ventilation unit so that theopening is also inclined with respect to the direction of air flow fromthe ventilation unit.